Device for removing dents

ABSTRACT

The invention is directed to a repair device for repairing a dent in a surface of a sheet metal structure. The repair device comprises a stand to be placed on the surface of the sheet metal structure, a pulling mechanism, which is connected to the stand, a welding head comprising at least one electrically conductive grounding connection and at least one electrically conductive pulling electrode, suitable to be welded to the surface of the sheet metal structure by a welding current. The welding current is generated by a welding machine. The pulling electrode is mechanically connected to the pulling mechanism such that the pulling electrode is movable by the pulling mechanism away from said surface.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention is in the field of repair technology of dents in sheet metal structures, e.g., of cars or airplanes.

[0003] 2. Related Art

[0004] From the state of the art several techniques to remove dents in sheet metal structure of cars are known. These techniques are in general based on attaching a load initiating element such as a pin or a wire on a metal surface to initiate a force to remove the dent. These load initiating elements are in general attached by special welding devices. After the load initiating element is applied the welding device is removed and a special repair tool such as a handle or a lever mechanism is attached to the load initiating element. One of the draw backs of the known techniques is that the process of applying the load initiating element is very time consuming and difficult and often causes further damage to the structure to be repaired. Therefore the results which can be achieved by the known technologies are in general not satisfying.

[0005] EP 0 544 191 describes a device for removing dents in a sheet metal structure. This device is suitable to be connected to a separate welding machine and a separate grounding connection.

[0006] A further technique is known for repairing dents in a sheet metal structures this device is used in combination with a pin like element. The pin like element is attached separately to the damaged sheet metal structure by welding. Afterwards a tool is connected to the pin like element to apply a force. The procedure is performed in steps and requires to attach and remove the pin like element repeatedly by a separated welding tool.

[0007] A further technique is known which is based on attaching a wire to the surface to be repaired such that a multitude of draw shackles are built. A special repair tool is attached to these draw shackles to pull out the dent. Attaching the wire is very time consuming.

SUMMARY OF THE INVENTION

[0008] The invention is directed to an improved repair device which incorporates a pulling and welding device for removing dents in a sheet metal structure in one tool. The repair device according to the present invention can be easily connected to and removed from a surface to be repaired. The repair device comprises one or more pulling electrodes that can be attached to the surface of a damaged sheet metal structure by one or more spot welding connections. The one or several pulling electrodes preferably can be arranged flexible depending on the size and the shape of the dent to be repaired. In contrast to the state of the art the repair device herein disclosed is made such that in general no separate grounding connection is necessary. The repair device preferably incorporates one or more grounding connections which are integrated in the repair device and arranged such that they are contacted to the surface of the damaged sheet metal structure close by a pulling electrode. The at least one pulling electrode and the at least one grounding connection are forming a unit which will be called from now on welding head. In the welding head the at least one grounding connection is arranged preferably adjustable in distance and orientation with respect to the at least one pulling electrode such that they can be contacted to different shapes of surfaces. The grounding connection can be built as a rigid or a flexible element.

[0009] A first preferred embodiment of the repair device has a welding head with a pin-like pulling electrode which is arranged substantially parallel at a distance between two pin-like grounding connections. The pin-like grounding connections are protruding over the pin-like pulling electrode and are arranged movable along their length axis such that they are backing up with a certain resistance if pressed against a curved surface. After the grounding element and the pulling electrode are in electrically conductive contact with the sheet metal structure a welding current is guided through the grounding connection and the pulling electrodes such that the pulling electrode is welded to the surface of the sheet metal structure. After applying a force which is directed such that the dent is reduced, the repair device is removed from the surface and if necessary reattached at a different location. The removal preferably takes place by twisting of or by rocking the repair device side wise.

[0010] In a second preferred repair device the pulling electrode is protruding over the grounding connections such that the pulling electrode is contacting the surface before the grounding connection is getting in contact. The repair procedure is similar to the preferred embodiment described above.

[0011] A pulling mechanism, preferably a lever mechanism or a electrical, pneumatic or hydraulic operated device, which is suitable to apply a pulling force is mechanically connected to the pulling electrode. This pulling mechanism is made such that a controlled pulling force can be applied in the main direction of the pulling electrode. The pulling mechanism can be built such that relationship of the levers is adjustable.

[0012] A third preferred embodiment of the repair device comprises an integrated welding device to generate a welding current. This hand held welding device has a handle to hold the device and a trigger to control the welding current. This embodiment has the major advantage that it is easy to use, simple and portable and without the need for a large and expensive separate welding machine. Therefore it is affordable for anybody.

[0013] The welding device can be incorporated in the stand of the repair device as shown in the figures. The hand held device typically has a front end with a welding adapter suitable to receive one or more pulling electrodes and a grounding adapter to be connected with a grounding connection such as described above.

[0014] In a welding head the electrical grounding contacts for the welding current are arranged preferably close to the pulling electrode such that it is not necessary to search for or to prepare a separate connection for contacting the negative terminal. Electrical contacts are preferably arranged that they are contacting the surface of the sheet metal structure at the same time or short after each other. By this arrangement best results are achieved and effort is minimized.

[0015] To reduce weight it is preferable to make the stand out of light weight metals, such as titanium or aluminum. Another preferred material is plastic, e.g. injection molded plastic reinforced by fibres which is easy to produce. In the case of plastic a separate isolation can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which like reference numerals indicate the same or similar components, and wherein:

[0017]FIG. 1 is a perspective view of a repair device illustrating the first embodiment of the repair device in accordance with the present invention;

[0018]FIG. 2 is a perspective view of a repair device illustrating the second embodiment of the repair device in accordance with the present invention;

[0019]FIG. 3 is a perspective view of a repair device illustrating the third embodiment of the repair device in accordance with the present invention; and

[0020]FIG. 4 is a perspective view of a repair device illustrating the forth embodiment of the repair device without a separate stand in accordance with the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021]FIG. 1 shows a preferred embodiment of a repair device 1 in a perspective view. The repair device 1 comprises a stand 2 with a pulling mechanism 3. An integrated hand held welding device 5 has a handle 6 to hold and a trigger 7 to control a welding current. The hand held device 5 typically has a front end section with an welding adapter 8 suitable to receive at least one pulling electrode 9 and a grounding adapter 10. The grounding adapter 10 has two elongated pin-like grounding connections 11 which are extending through isolated openings in a holding bar 12. The pulling electrode 9 is arranged essentially parallel to the pin-like grounding connections 11 arranged at a distance d. As it can be seen the pulling electrode 9 has a tip 20 which is projecting over the two grounding connections 11. The grounding connections 11 and the pulling electrode 9 are part of a welding head 14.

[0022] The grounding connections 11 are mounted on first isolating bearings 21 which are built such that the grounding connections 11 are displaceable along their length axis (z-axis). On the upper side spring elements 23 are arranged around the grounding connections between the grounding adapter 10 and the holding bar. The spring elements 23 oppose a certain resistance against a relative movement between the holding bar 12 and the grounding connections 11. The upper position of the grounding connections 11 is defined by a splint fastener 13 (not visible) which is arranged around each of the grounding connections 11 on the lower side of the holding bar 12. As an alternative adjusting screws can be used to adjust the position.

[0023] The pulling electrode 9 extends through the holding bar 12 guided by a second bearing 25 and is support elastically in the welding device 5 such that it can be moved relative to the welding device 5 and the grounding connections 11. A spring element (not visible) is arranged on the upper end of the pulling electrode 9 in the welding device 5. It presses the pulling electrode downward and opposes a certain force if the pulling electrode is pressed into the welding device 5.

[0024] On both ends of the holding bar 12 two vertical standlegs 26 are arranged extending in a perpendicular angle from the horizontal holding bar 12. Each standleg 26 has on it's free end a base element 27. The base elements 27 are shown here as two bar-like elements. Alternatively they can be built out as base elements adjustable in orientation and arrangement. From the holding bar 12 an arm 30 extends in an approximately vertical direction (−y-axis). The arm 30 incorporates a hinge element 31 which bears a lever 32. The lever 32 is on it's front end mechanically connected to the pulling electrode 9. On their rear ends the arm 30 and the lever 32 have handles 33. The lever 32 and the arm 30 are part of a pulling mechanism 3 which is use to pull the pulling electrode upwards (+z-direction) to remove the dent.

[0025] To remove a dent in a sheet metal surface the welding head 14 of the repair device 1 is placed over the damaged area resting on it's base elements 27. Then the welding head 14 together with the grounding connections 11 and the pulling electrode 9 are pushed down such that the spring elements 23 are compressed and the pulling electrode 9 is getting in contact with the surface of the sheet metal structure. By further pressing the welding device 5 down, the pulling electrode 9 is pressed into the welding device 5 and the grounding connections 11 are getting in contact with the sheet metal structure. When a conductive connection between the sheet metal structure and the pulling electrode 9 and the grounding elements 11 is achieved a welding current generated by the welding device 5 is guided through the sheet metal structure, the pulling electrode 9 and the grounding elements 11 such that the pulling electrode 9 is spot-welded to the surface of the sheet metal structure. The welding current is control by the trigger 7 which is arranged here in the handle 6 of the welding device 5.

[0026] After the pulling electrode 9 is connected to the surface of the sheet metal structure to be repaired, the handle 33 of the lever 32 is pressed against the handle 33 of the arm 30 such that the pulling electrode is moved upwards (+z-direction) with respect to the holding bar 12. By this action the surface of the sheet metal structure is pulled upwards and the dent will be at least partially removed.

[0027] To remove the pulling electrode 9 from the surface of the sheet metal structure the pulling electrode 9 is twisted or rocked sideways.

[0028] In a still further embodiment the grounding connections 11 are protruding over the pulling electrode 9 such that when attaching the repair device 1 to a damaged surface the grounding connections 11 are getting first in contact to the surface of the sheet metal structure. The welding device 5 is preferably arranged movable around it's height axis (z-direction). If necessary the welding device can be build detachable from the grounding adapter 10 and the pulling electrode 9.

[0029] The pulling electrodes 9, respective the grounding elements 11 preferably are exchangeable or have exchangeable tips which can be replaced if worn. The material of the pulling electrode is chosen depending of the material of the sheet metal structure to be repaired.

[0030]FIG. 2 shows a further embodiment of a repair device 1 with a stand 2 having three supporting arms 4 extending in a radial direction. Each of the supporting arms 4 has a slot 40 with a standleg 26 having an adjustable base element 27. The standlegs 26 can be shifted along the slots 40 and locked by wing nuts 41. As it can be seen instead of a welding device the repair device 1 incorporates a plug 35 suitable to connect an external welding machine as known from the state of the art. The plug 35 is connected to the grounding connections 11 and the pulling electrode 9 and is preferably made such that the repair device 1 is compatible with several welding machines. The repair device 1 preferably has a switch (not displayed) to control the welding current.

[0031] The welding head 14 with the pulling electrode 9 which is arranged between two grounding connections 11, and the grounding connections 11 are mounted in first and second linear bearings 21, 25. The grounding connections are connected by a ring-like base element with an annular connecting surface 15.

[0032] The upper end of the pulling electrode 9 is arranged in a knob 42 which incorporates the plug 35. On the lower end of the knob 42 a grounding adapter 10 can be seen. In this grounding adapter 10 the grounding connections 11 are mounted flexible such that they can move relatively to the grounding adapter 10 when knob 42 is pressed down and the grounding connections are getting in contact with a surface. In stead of the arrangement shown here it is possible to implement more or less then two grounding connections. The grounding connections are in general arranged at a distance to the pulling electrode 9 such that they are forming a conductive connection with the sheet metal surface. Therefore no additional connection is needed. An arrangement wherein the grounding connections 11 are getting in contact with a surface covered e.g. by paint is not suitable.

[0033] As it can be seen the pulling electrode 9 of this welding head 14 extends over the grounding connections 11. When the repair device 1 is placed over a dent, and the knob 42 is pressed down in the direction of the sheet metal structure, the spring elements 23 are compressed and the grounding connections 11 are getting in contact with the damaged surface. By further pressing the knob down, the grounding elements are pressed into the grounding adapter 10 and the pulling electrode 9 is further pressed down until it gets also in contact with the surface of the sheet metal structure. When a conductive connection is obtained a welding current is guided through the device until the pulling electrode is connected to the surface. By pressing the handles 33 of the pulling mechanism 3 together the pulling electrode 9 is moved in opposite direction and the dent is at least partially removed.

[0034] To separate the pulling electrode 9 from the surface the whole repair device 1 is twisted around the length axis of the pulling electrode 9. In an alternative embodiment the welding head 1 can be arranged such that it can be turned around it's length axis independent of the rest of the repair device 1.

[0035]FIG. 3 is showing another repair device 1 having a welding device 5 incorporated. Instead of a pulling electrode the herein shown welding head 14 has a pulling device 45. The pulling device 45 comprises in this embodiment three pulling electrodes 9 arranged on one line (other arrangements are possible). The pulling electrodes are arranged flexible in their length direction such that they can be brought in contact with a curved surface at the same time. They also can be mechanically connected to each other such that a pulling force is distributed among them equally. The pulling electrodes 9 are connected consecutively with the welding machine. If necessary the pulling electrodes 9 can be welded at the same time to the surface of the sheet metal structure or after each other such that the full capacity of the welding device is available for each spot welding connection. The sequence of the applied welding current is preferably controlled by a mechanical or electrical switch. Due to the several pulling electrodes it is possible with this third embodiment to apply more force to a surface of a sheet metal structure.

[0036] The repair device 1 has a stand 2 with three vertical standlegs 26 which are adjustable in distance with respect to the welding head 14. Each of the standlegs 26 has a base element 27 which is built that it's orientation is adjustable. As an alternative or in addition to it is possible to build the base elements 27 conductive such that they are suitable to serve as grounding connection. To apply such a solution successfully in repairing dents it would be necessary to guarantee that the surface of the sheet metal structure to repair is blank and electrically conductive in the area the base elements 27 are placed. In stead of two base elements 27 it is also possible to have one larger base plate having an opening in the area where the pulling electrodes 9 have to be placed on a surface. This base plate can be build conductive such that it is suitable to serve as a grounding connection.

[0037]FIG. 4 shows a further embodiment of the repair device 1 with a welding head 14. In the repair device 1 a hand held welding device 5, e.g. as known from the state of the art, is incorporated. The repair device 1 has a stand 48 in which the grounding connection is integrated. The stand 48 has in this embodiment an annular connecting surface 50 on it's lower end which can have a different shape or it can comprise protruding contact elements, e.g. made of highly conductive material (not visible) which are serving as grounding connections.

[0038] The stand 48 has a clamp 49 on it's upper end which fits around the grounding adapter 10 of the welding device 5. It can be separated from the welding device 5 by releasing a clamping screw 51. The stand 48 has a pulling mechanism 3 with two handles 33. The pulling mechanism is mechanically connected to the pulling electrode 9 by an insolating element 52. By pressing the handles 33 together the pulling electrode is pulled upwards.

[0039] To repair a dent the repair device 1 is set with it's annular connecting surface 50 on to the damaged area and the pulling electrode 9 is brought in contact with the damaged surface. After the pulling electrode 9 is spot welded to the surface, the levers 33 are pressed together such that the pulling electrode is pulled upward whereby the dent is minimized. The pulling electrode 9 is released by twisting or sideward moving of the repair device 1 or by twisting of the pulling electrode only. The pulling electrode 9 is made such that it can be replaced easily. Instead of the lever mechanism 3 an automated, e.g. pneumatic, hydraulic or electric driven pulling device can be used to pull the pulling electrode 9 upwards and/or to release the pulling electrode 9 from the surface. The pulling electrode is preferably arranged flexible with respect to it's length axis and pushed forward e.g. by a spring element. Other arrangements or arrangements with more than one pulling electrode to increase the applicable force are possible. Due to the grounding connection integrated in the stand 48 the repair device 1 is easy to use, fast and reliable. A major advantage of the here shown embodiment is that no separate grounding connection needs to be attached additionally.

[0040] Although the preferred embodiments of the present invention have been described, it will be understood by those skilled in the art that the present invention should not be limited to the described preferred embodiment. Rather, various changes and modifications can be made within the spirit and scope of the present invention, as defined by the following claims. 

What is claimed is:
 1. A Repair device for repairing a dent in a surface of a sheet metal structure comprising a stand to be placed on the surface to be repaired, a pulling mechanism which is connected to the stand, a welding head comprising at least one electrically conductive grounding connection and at least one electrically conductive pulling electrode, suitable to be welded to the surface of the sheet metal structure by a welding current generated by a welding machine, said pulling electrode being mechanically connected to the pulling mechanism such that the pulling electrode is with respect to the stand movable by the pulling mechanism away from said surface.
 2. The repair device according to claim 1, having a hand held welding device integrated.
 3. The repair device according to claim 1, having a connection for an external welding device.
 4. The repair device according to claim 1, wherein the pulling mechanism is driven by one of a manual, electrical, hydraulic or pneumatic source of motive power.
 5. The repair device according to claim 1, wherein the stand is a rigid construction comprising a holding bar with at least one standleg and the welding head comprises at least one pulling electrode and at least one grounding connection arranged movable with respect to the stand whereby they can be brought in electrically conductive contact with the surface of the sheet metal structure.
 6. The repair device according to claim 5, wherein the stand has at least two standlegs.
 7. The repair device according to claim 6, wherein the standlegs are adjustable in distance and orientation with respect to the welding head.
 8. The repair device according to claim 5, wherein the welding head has a pin-like pulling electrode arranged substantially parallel between two pin-like grounding connections.
 9. The repair device according to claim 5, wherein the grounding connection has a annular connecting surface.
 10. The repair device according to claim 5 with a pulling device incorporating multiple grounding connections.
 11. The repair device according to claim 10, wherein the grounding connections are arranged in one line.
 12. The repair device according to claim 1, wherein the grounding connection is incorporated in the stand.
 13. The repair device according to claim 12, wherein the stand has a annular connecting surface. 